Automatically adjusting patella cutting guide

ABSTRACT

A patella clamping device has a handle having a first arm and a second arm, the first and second arms each having a first gripping end and a second clamping end. The clamping end of each arm is movable towards the opposite arm by action on the gripping end of each arm. The clamping end of the first arm comprises a clamping surface opposed to a clamping surface on the clamping end of the second arm. The clamping end of each arm has a body portion having spaced first and second surface defining the opposed surface of each arm. A plurality of pins extend from the first surface to the second surface on each arm clamping end. A rotatable toothed jaw member is pivotally mounted on each of the pins. The jaw member has at least one tooth extending outwardly of the opposed surface of each arm for engaging the patella. Each body has a third surface spaced from the second surface to create a slot for receiving a saw blade.

BACKGROUND OF THE INVENTION

The invention relates to a patellar saw guide which has a plurality ofrotatable teeth adapted to engage an edge of a patella prior to itspreparation for receiving a prosthetic implant.

A patellar clamp and saw guide are used during a total knee arthroplastyprocedure to prepare the posterior surface of a patellar bone to accepta prosthetic implant.

Typically, a surgeon will select a patellar prosthesis for implantationeither by utilizing a resurfacing technique wherein the prostheticpatella will be resected and resurfaced and/or by an insetting procedurewhere the prosthetic patella is inserted into the prepared surface ofthe patella.

The patella is a sesamoid or lens shaped bone which slides in a groovebetween the condyles of the femur. Its function is to increase theefficiency of the quadriceps muscle by shifting the line of action ofthe muscle's pull forward. As the knee articulates, the muscles andtendons force the patella toward the condyles of the femur.Consequently, there is considerable relative motion between the patellaand the other bones comprising the knee joint.

Because of aging or disease, the articulating surfaces of the knee maydegrade. To treat certain pathologies, it has become common tosurgically remove the condyles and replace these structures withprosthetic implants. By the same processes, the articulating surfaces ofthe patella may also degrade. In connection with the implantation of aprosthetic knee, therefore, the articulating surface of the patella mayalso be replaced. Because of the tendons connected to the patella, it isgenerally advisable to replace only the articulating surfaces. An ultrahigh molecular weight polyethylene articulating surface, with or withouta metal baseplate or metal backing, will be implanted on the posteriorside of the patella, adjacent the femoral condyles.

In either a total resurfacing procedure or a patella insettingprocedure, it is important that a sufficient amount of bone stock remainafter resection to accept the typical fixation pegs of the patellarprosthesis and maintain the integrity of the remaining patellar bone.Therefore, proper location of the saw blade is important.

As used herein, when referring to bones or other parts of the body, theterm “proximal” means closer to the heart and the term “distal” meansmore distant from the heart. The term “inferior” means toward the feetand the term “superior” means towards the head. The term “anterior”means towards the front part of the body or the face and the term“posterior” means towards the back of the body. The term “medial” meanstoward the midline of the body and the term “lateral” means away fromthe midline of the body.

Prior art devices for aiding the surgeon in performing patellaresections are well known to those skilled in the art. For example,Peterson, in U.S. Pat. No. 4,673,862, teaches a method and instrumentsfor the installation of a patella button prosthesis which involvesperforming a patella resection.

In particular, Peterson relates to a saw guide which comprises apliers-like instrument having a pair of mutually pivotable jaw members.The jaw members are designed so as to enable them to surround part ofthe outer periphery of the patella with each jaw member having arespective handle, integrally formed therewith, which handles may bepivoted so as to pivot the jaw members to and from engagement with partof the patella periphery. The Peterson device requires that a flat sawblade be guided over the face of the jaw members after the patella hasbeen set to the correct depth between the members.

U.S. Pat. No. 5,147,365 relates to a patella osteotomy guide in whichthe jaw members include a slot for guiding the flat saw blade and an armfor setting the saw blade depth in the patella.

U.S. Pat. No. 5,486,177 relates to a patella milling instrument having aclamp which contacts the underside of the patella. A similar clampingtool is shown in U.S. Pat. No. 5,284,482.

U.S. Pat. No. 5,222,955 relates to a reaming system designed to cut aconical bore in a patella surface while the patella is being held in apatella clamp similar to that disclosed in U.S. Pat. No. 5,284,482. U.S.Pat. No. 5,941,884 relates to a patella clamp which includes indicia ofboth the amount of bone resected and the amount of bone remaining.

BRIEF SUMMARY OF THE INVENTION

It is one aspect of the invention to provide an improved apparatus andmethod for facilitating the preparation of the natural patella toreceive a patellar prosthesis.

It is an additional aspect of the invention to provide a clamping systemwhich can hold the patella in position during resection by actuating apliers like grip.

The cutting guide of the present invention has the ability to clampvariously shaped patellae by automatically adjusting the direction ofthe clamping teeth to the anatomy of the patella. The intention of thisdesign is to automatically adjust to the edge surface of variouslyshaped patellae to provide a more secure hold.

The invention works by clamping the patella jaws over the patella bonewith multiple teeth embedded in the patella. The patella jaws secure thepatella sufficiently to allow a surgeon to use an oscillating surgicalsaw to resect the patella bone in a well known manner.

The clamping tooth or teeth are located on a plurality of rotatableelements that rotate about a pin such that the teeth will align with thepatella edge surface resulting in more holding teeth penetrating thepatella bone. The clamp may also have a slot to guide an oscillatingsurgical saw to cut the clamped patella.

The rotation of the toothed rotatable element is limited by stops placedin a top and/or bottom portion forming the automatically adjustingpatella cutting guide. These stops in combination with the stop featurescut into each toothed rotatable element limit the amount of rotation ofeach toothed rotatable element. This limit prevents the 360° rotation ofthe toothed element about the pin which would allow the teeth to rotateout of contact with the patella bone.

The patella clamping device of the invention has a handle portion havinga first arm and a second arm which arms may be coupled by a pivot pin ora linkage system which preferably moves the arms in parallel. The firstand second arms each have a first gripping end and a second clampingend. The clamping end of each arm is movable, such as by the pivoting orlinkage action, towards the opposite arm by movement of the gripping endof each arm towards one another. The clamping end of the first arm has aclamping surface opposed to a clamping surface on the clamping end ofthe second arm. The clamping end of each arm includes a body portionhaving spaced first and second surfaces and a plurality of pinsextending from the first surface to the second surface on each armclamping end. One toothed rotatable jaw member is pivotally mounted oneach of the plurality of pins. The rotatable jaw members each have atleast one tooth extending outwardly of the opposed surface of each armtowards the opposite arm clamping surface. The opposed clamping surfaceon the clamping arm defined by the body portion may be arcuate with aconcave surface facing towards the patella gripping area. Each bodyportion preferably has three pins and toothed rotatable jaw members.Each jaw preferably has three teeth but fewer or more teeth can be used.To improve gripping at least two teeth on each jaw may have a differentsize or shape. Each body portion may include a stop element adjacenteach toothed jaw member to limit the rotation of each toothed rotatablejaw member around the pin. The stop member may be a raised portion on atleast one of the first and second surfaces adjacent a recessed sidesurface of the toothed jaw member. The first and second clamping armbodies have a surface for guiding a saw blade.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric view of a patella clamp including theautomatically adjusting clamps of the present invention;

FIG. 2 is a plan view of the clamping end of the clamping device of FIG.1 gripping the peripheral edge surfaces of a patella;

FIG. 3 is an enlarged view of the two patella clamps shown in FIG. 2detached from the clamping device of FIG. 1;

FIG. 4 is a plan view of a bottom portion of each clamp arm of FIG. 3;

FIG. 5 is an elevation view of the clamping arm bottom portion shown inFIG. 4;

FIG. 6 is a bottom view of the clamping arm bottom portion of FIG. 4;

FIG. 7 is a top view of a clamping arm top portion as shown in FIG. 3;

FIG. 8 is an elevation view of the clamping arm top portion shown inFIG. 7;

FIG. 9 is an isometric view of a rotatable toothed element for mountingbetween the bottom clamping arm portion of FIG. 4 and the top clampingarm portion of FIG. 7;

FIG. 10 is a cross-sectional view through lines X-X of FIG. 9;

FIG. 10 a is an alternate embodiment of the rotatable toothed elementwherein the hole is moved outward of the center line of the element toallow more rotation of the teeth inwardly;

FIG. 11 is a top view of an assembly of the clamping arm bottomportions, top portion and toothed element of FIGS. 4, 7 and 9respectively;

FIG. 12 is a bottom view of the assembly FIG. 11;

FIG. 13 is a cross-sectional view of the clamping arm member shown inFIG. 11; and

FIGS. 14 and 15 show alternate embodiments of jaw rotation stopelements.

DETAILED DESCRIPTION

Referring to FIG. 1, there is shown a patella clamping device generallydenoted as 10 which includes a handle portion including two grippingmembers 12 and 14. Gripping members 12 and 14 engage a pivot section 16which is capable of moving a first jaw arm 18 towards a second jaw arm20. Pivot section 16 may include one or more pivot pins and /or alinkage system for transferring the action or gripping member 12, 14 tojaw arms 18, 20. The linkage system may move jaw arms 18, 20 inparallel. The jaw arms 18 and 20 may be removably coupled to clampingsection 16. The handle portion and pivot section of the patella clampingdevice 10 are known in the prior art and are shown, for example, in U.S.Patent Application Publication No. 2007/0118141, the disclosure of whichis incorporated herein by reference.

Referring to FIG. 2, there is shown a top view of the two clamping jawarms 18 and 20 surrounded and clamping a patella 24. Arms 18 and 20 arearcuate and have concave surfaces 26 and 28 respectively facing inwardlytowards patella 24 which arms include rotatable toothed jaw elements 30a, 30 b and 30 c which will be discussed in more detail below. Arms 18and 20 may be separate elements which can be selectively coupled ordetached from pivot section 16. Referring to FIG. 3, there is shown theclamping jaw arms 18 and 20 detached from the handle portion of clampingdevice 10. At the end mounted on the handle 10 there are couplingelements 32 and 34 designed to couple the clamping jaw arms to thehandle 10 in a selectively releasable manner. Preferably two springloaded detent mechanisms (not shown) which respectively engage recessedportions 33 and 35 of elements 32 and 34 are mounted in ends 17 and 19of pivot section 16. Obviously the jaws could be fixedly attached to thehandle 10. However, providing a releasable coupling mechanism allows fordifferent size clamping jaws to be used depending on the size of apatella. Preferably each clamping arm 18, 20 includes a series of threepivotable tooth elements 30 a, 30 b and 30 c each having, in a preferredembodiment, three teeth.

Referring to FIGS. 4-8, there is shown bottom portion 40 (FIGS. 4-7) andtop portion 42 (FIGS. 7 and 8) respectively which, when assembled, formclamping jaw arms 18 and 20. Only one claiming jaw 18 is described.Clamping jaw is identical in design but concave in the oppositedirection. Thus clamping jaw arms 18 and 20 are mirror images. Referringto FIG. 4, there is shown a top view of bottom portion 40 of clampingjaw arms 18 and 20 including coupling element 32. Bottom portion 40includes three raised areas or bosses 44, 46 and 48 which have agenerally triangular shape with the apex directed towards the concavesurface 26 of the arm 18. Each boss 44, 46 and 48 has a bore 50, 52 and54 respectively which may be located on a centerline of the raised areasadjacent the apex which bores are adjacent concave surface 26. Thebosses 44, 46 and 48 can be seen in FIG. 5 which is an elevation view ofjaw arm 18 of FIG. 4. Also visible in FIG. 5 is a cutting blade slot 56below an upwardly facing surface 41 of bottom portion 40. Slot 56 mayreceive an oscillating saw blade (not shown) adapted to resect thepatella in a well known manner.

As best seen in FIG. 5 bosses 44, 46 and 48 are separated by gaps 60 and62 which gaps widen on moving from the outer surface 31 of jaw arm 18 tothe inwardly facing surface 26 of bottom portion 40 of arm 18. Referringto FIG. there is a bottom view of jaw arm 18 bottom portion 40 showingbores 50, 52 and 54 as well as a recessed edge 66 which defines an uppersurface 55 of slot 56.

Referring to FIGS. 7 and 8 there is shown top portion 42 of clamping jawarm 18. Top portion 42 includes a downwardly facing surface 68 whichincludes three bosses 70, and 74 which again are generally triangular inshape and match the shape of bosses 44, 46 and 58. The apexes of bosses70, 72 and 74 are adjacent concave surface 26 and wider portionsadjacent outer surface 31. Three pin holes 76, 78 and 80 are locatedadjacent the apex on each boss. Top portion 42 includes three smallholes 82 designed to receive holding pins which connect the bottom andtop portions (40, 42) of arms 18 and 20 such as by spot welding ordeformation. Top portion 42 does not include a coupling element 32 andgenerally acts to mount and capture rotatable toothed jaw elements 30 a,30 b and 30 c.

Each of the generally triangular shaped bosses 44, and 48 and 70, 72 and74 can be aligned prior to the assembly of the top and bottom portionsto form clamping jaw arm 18. Thus, each aligned pair of bosses haveidentical angled sides 90 and 92 so that upon assembly a smooth sidesurface of the aligned bosses result. When bosses 44, 46 and are alignedrespectively with bosses 70, 72 and 74 holes 50, 52 and 54 are alsoaligned with holes 76, 78 and 80 so that they may receive a pivot pin112. Side surfaces 90 and 92 of each of the six bosses are angled atbetween 40 and 45 degrees and spaced to form gap 60 and 62. These anglescan change based on teeth size and boss size. For example, a larger bosswould create a smaller angle. In a preferred embodiment, the alignablebosses 44 and 70 as well as alignable bosses 46 and 72 have sides 90 and92 angled at 45 degrees while alignable bosses 48 and 74 having an angleof sides 90 and 92 of 40 degrees. In addition, the lengths of sides 90and 92 of the bosses may vary depending on the location of alignableholes 50, 52, 54 and 76, 78 and 80 which holes, when the top and bottomportions 40 and 42 are assembled, align to receive a pivot pin as willbe discussed below.

FIG. 8 is an elevation view of top portion 42 of FIG. 7 showing bosses70, 72 and 74 spaced by gaps 60 and 62.

Referring to FIGS. 9 and 10, there is shown one of the rotatable toothedelements 30 a, 30 b and 30 c each including three teeth 100. While threeteeth 100 are shown, any number of teeth can be utilized. FIG. 9 showsone of the toothed element 30 a, 30 b and 30 c which may be identicaland is designated as 30 including a bore 102 for receiving a pivot pinand a recessed generally triangular area 104 facing an upper surface 106and, as seen in FIG. 10, a bottom recessed generally triangular area 108facing a bottom surface 110. Bore 102 may be located on a centerline ofa toothed element 30 a, 30 b and 30 c. However, as shown in FIG. 10 a,an alternate toothed element 130 may have a bore 102 a offset from acenterline 103 a so that greater inward rotation of teeth 100 a ispermitted. This result can also be accomplished by leaving bore 102 a inthe center but offsetting the pivot pin holes 76, 78 and 80 in thebosses.

Toothed elements 30 a, 30 b, 30 c and 130 are adapted to be mountedbetween the top and bottom members 40, 42 of clamping jaw arms 18, 20.The top and bottom recessed areas 104 and 108 are shaped to receivebosses 44, 46, 48 and 70, 72 and 74 when the top and bottom jaw armportions 40, 42 are assembled. However, the generally triangularlyshaped recessed areas 104, 104 a and 108 of toothed elements 30 a, 30 b,30 c and 130 are at a wider angle than the 40 to 45 degree includedangle of sides 90 and 92 of each boss 44, 46, 48, 70, and 74 thusallowing limited rotation of the toothed elements about pivot pin 112mounted through holes 50, 52, 54 and 76, 78, 80 respectively and bore102. The sides of the bosses act as stop surfaces so that toothedelements 30 a, 30 b, 30 c and 130 cannot rotate out of engagement withthe patella.

Referring to FIGS. 11-13, there is shown the assembled clamping jaw arms18 or 20 whereby bottom portion and top portions 40, 42 are assembledcapturing toothed elements 30 a, 30 b and 30 c therebetween. Holdingpins (not shown) extending through holes 82 may be spot welded to eachtop and bottom portion 40, 42 to capture toothed element 30therebetween. Three pivot pins 112 are inserted through holes or bores76, 78 and 80 of top portion 42, through bore 102 of each toothedelement 30 a, 30 b, 30 c and into bores 50, 52 and 54 of bottom portion40. Pins 112 may be spot welded to top member 42. Pins 112 extendpartially into bottom member 40 stopping prior to slot 56 thus leavingthe slot 56 open to receive an oscillating saw blade (not shown).

In use, clamping jaw arms 18 and 20 are mounted on portion 16 ofclamping device 10 and handles 12 and 14 are actuated to clamp theclamping jaw arms 18, 20 around a patella. Upon contacting an edgesurface of the patella, at least one of the three toothed jaw elementson each clamping arm 18 and 20 will pivot automatically into a positionengaging the periphery of patella 24. Thus, a plurality of teeth 100from one or more of the tooth elements will contact each side of theperiphery of the patella.

The teeth 100 of toothed elements 30 a, 30 b, 30 c or 130 may be madeeither identically or may vary in size either on each toothed element 30a, 30 b and 30 b or from one toothed element to another. Again thisenhances the ability to have multiple teeth 100 contacting the edge ofpatella 24. Once the patella 24 is gripped, a resection may be performedwith an oscillating saw in a standard manner.

Referring to FIG. 14, there is shown a jaw member 230 similar to jawmembers 30 a, 30 b and 30 c mounted on an arm 18, 20 in a recess 232formed thereon. The recess 232 is similar in shape to the bossesdescribed above. Jaw 230 is again rotatable on a pivot pin 234 withcontact between sides 236 and 238 of jaw member 230 and sides 240 and242 of recess 232 acting as a stop system for the rotation of jaw 230about pivot pin 234.

Referring to FIG. 15, there is shown a jaw member 330 mount on an arm18, 20 rotatable about a pivot pin 334. In this embodiment there are nobosses or recesses but only two pins 336 and 338 for contact sidesurfaces 340 and 342 of jaw 330 to act as stop elements. Pins 336 and338 would be fixed to members 40 and 42 and extend between surfaces 41and 68 thereof.

Although the invention herein has been described with reference toparticular embodiments, it is to be understood that these embodimentsare merely illustrative of the principles and applications of thepresent invention. It is therefore to be understood that numerousmodifications may be made to the illustrative embodiments and that otherarrangements may be devised without departing from the spirit and scopeof the present invention as defined by the appended claims.

1. A patella clamping device comprising: a handle having a first arm anda second arm, the first and second arms each having a first gripping endand a second clamping end, the clamping end of each arm movable towardsthe opposite arm by action on the gripping end of each arm, the clampingend of the first arm having a clamping surface opposed to a clampingsurface on the clamping end of the second arm, the clamping end of eacharm comprising a body portion having spaced first and second surfaces,at least one pin extending from the first surface to the second surfaceon each arm clamping end; and a jaw member pivotally mounted on each ofthe pins, the jaw member having at least one tooth extending outwardlyof the opposed surface of each arm.
 2. The patella clamping device asset forth in claim 1 wherein the opposed clamping surface defined by thebody portion is arcuate.
 3. The patella clamping device as set forth inclaim 1 wherein each body portion has three pins and jaw members.
 4. Thepatella clamping device as set forth in claim 3 wherein each jaw hasthree teeth.
 5. The patella clamping device as set forth in claim 4wherein at least two teeth on each jaw have a different size.
 6. Thepatella clamping device as set forth in claim 1 wherein each bodyportion includes stop element adjacent each jaw member to limit therotation of each jaw member around the pin.
 7. The patella clampingdevice as set forth in claim 6 wherein the stop member is a raisedportion on at least one of the first and second surfaces adjacent a sidesurface of the jaw member.
 8. The patella clamping device as set forthin claim 7 wherein the raised portion has a triangular shape.
 9. Thepatella clamping device as set forth in claim 8 wherein the jaw memberhas a generally triangularly shaped recessed area for receiving theraised portion on the stop element.
 10. The patella clamping device asset forth in claim 9 wherein a pivot pin engages the jaw member adjacentan apex of the generally triangular recessed portion.
 11. The patellaclamping device as set forth in claim 9 wherein a pivot pin engages thejaw member at a location offset from a centerline through the teeth. 12.The patella clamping device as set forth in claim 1 wherein each bodyhas a third surface for guiding a saw blade.
 13. A patella clampingdevice comprising: first and second opposed arcuate patella grippingarms each having a concave surface facing the opposed arm; a pluralityof toothed jaw members pivotally mounted on each of the first and secondarcuate patella gripping arms, the teeth on each jaw member extendinginwardly towards the opposed facing concave surfaces of each arm; and ameans for moving the opposed first and second gripping arms toward oneanother.
 14. The patella clamping device as set forth in claim 13wherein the first and second opposed gripping arms have three jawmembers pivotally mounted thereon.
 15. The patella clamping device asset forth in claim 14 wherein each jaw member has three teeth.
 16. Thepatella clamping device as set forth in claim 13 wherein each of thefirst and second opposed clamping arms has a slot for guiding a sawblade.
 17. The patella clamping device as set forth in claim 13 whereinthe first and second opposed clamping arms include a stop surface forlimiting the pivotal movement of the jaw member pivotally mountedthereon.
 18. The patella clamping device as set forth in claim 17wherein the means for moving the opposed first and second clamping armstowards one another is a linkage which moves the arms while maintainingthem in parallel.